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JAMA Facial Plastic Surgery Guide to Statistics and Methods
Jul/Aug 2015

Thoughtful Methods to Increase Evidence Levels and Analyze Nonparametric Data

Author Affiliations
  • 1Department of Otolaryngology–Head and Neck Surgery, Johns Hopkins School of Medicine, Baltimore, Maryland
JAMA Facial Plast Surg. 2015;17(4):307-308. doi:10.1001/jamafacial.2015.0465

In this issue of JAMA Facial Plastic Surgery, Sapthavee et al1 present a retrospective cohort study designed to compare the effectiveness of skin graft reconstruction and local flap reconstruction for nasal defects. This article is an excellent example of how level of evidence (LOE) can be increased from level 4 (case series) to level 3 (retrospective cohort study) by adding a comparison cohort group to the analysis (Table 1).2 It is also a good example of using a nonparametric statistical test, the Wilcoxon rank sum test, to evaluate nonparametric data.